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[en] This paper highlights an investigation on the comparative analyses of exergetic performance with optimum volume concentration of hybrid nanofluids in a plate heat exchanger (PHE). Different types of hybrid nanofluids (Al2O3 + MWCNT/water, TiO2 + MWCNT/water, ZnO + MWCNT/water, and CeO2 + MWCNT/water) as coolant have been tested. Proportion of 0.75% of nanofluid has been found to be the optimum volume concentration. The requisite thermal and physical properties of the hybrid nanofluids were measured at 35 °C. Various exergetic performance parameters have been examined for comparing different hybrid nanofluids. The highest reduction in exergy loss of CeO2 + MWCNT/water hybrid nanofluid has been obtained at a concentration of about 24.75%. Entropy generation decreased with the increase in volume concentration. The results established that CeO2 + MWCNT/water hybrid nanofluid can be a promising coolant for exergetic performances in a PHE. (paper)
[en] Full text: Natural circulation has an important role in long term cooling of a nuclear reactor during a loss of coolant accident or after an emergency shut down of the plant. An experimental study of steady state behavior for single-phase rectangular natural circulation loop with water as the working fluid was conducted. Measurement of the water temperature distribution around the loop was made under the on/off cooling system and with the different heating power levels. The results show that at the same heating power level, the water temperature is much higher when cooling system was turned off. However, the same temperature differences across the heater were measured with the cooling system being turned on and being turned off. In addition, the mass flow rate due to a density gradient was calculated
[en] Highlights: ► We evaluate the suitability of 11 empirically performance models for centrifugal water chillers. ► The prediction accuracy of each model is based on CV values. ► The evaluation for model suitability is based on five indexes. ► The BQ, MP, SMP, and MDOE-2 models have good prediction accuracy. ► The BQ, MP, and SMP models have the best suitability. - Abstract: This study evaluates the performance prediction ability and model suitability of eleven empirically-based performance models for centrifugal water chillers. Specifically, this study uses over 2000 datasets with a constant or variable chilled water flow rate for fixed or variable speed drive centrifugal liquid chillers. The best regression coefficients for each empirical-based model were obtained using the ordinary least squares (OLSs) method. The model prediction accuracy of each empirical-based model is based on the coefficient of variation of root-mean-square error (CV). The evaluation for model suitability is based on the considerations of prediction ability, the complexity in training datasets, the effort needed to calibrate, the generality of the model, and its ability to physically interpret the model regression coefficients in this study. Results show that among the eleven empirical-based models, the BQ (CV = 0.54%), MP (CV = 0.61%), SMP (CV = 0.70%), and MDOE-2 (CV = 0.63%) models have overall prediction CV values under 1% for all kinds of datasets and achieve extremely good prediction accuracy. Because the MDOE-2 model has a more complicated datasets training process than the BQ, MP, and SMP models, and it has no ability to physically interpret the model regression coefficients, the BQ, MP, and SMP models have the best suitability. The results of this study provide important reference values for selecting empirically-based performance models for energy analysis, optimal operating control, energy efficiency measurement and verification (M and V), and the development of fault detection and diagnosis (FDD) systems in centrifugal water chillers.
[en] Electricity crisis condition happened in West Kalimantan (Kalbar) as a result of power plant capacity almost equal to the peak load. The system will experience a shortfall if there are plants that not operating and do not have reserve. The policy of electricity planning until 2022 is replacing diesel power plant with steam power plant. For long-term planning is required the role of new and renewable energy in order to reduce dependency on fossil fuel consumption, such as NPP utilization. The purpose of this study was to determine the optimum location of the NPP power distribution in order to prepare electricity infrastructure. Load flow calculation in this study using ETAP 12.5 software. NPP is planned to supply base load, so the optimum capacity factor is above 80 %. The result show that there are three location where NPP can generate over 80 % of its capacity, namely: Mempawah Substation, Singkawang Substation, and Sambas Substation. The most optimum located in Mempawah Substation with capacity factor 83.5 %. The location of the three Substation are onshore and in line with one requirement for NPP construction, namely: the availability of cooling water. (author)
[en] Operation of Radioactive Waste Installation (RWI) process supporting facilities is media and energy provider services for radioactive waste processing activities, research and administration in PTLR consists oj- steam system, cooling water for evaporators, compressed air system for pneumatic control of the entire process system, water chiller (chilled water system) for air system and process unit, service water system for processing and offices, demineralized water system, VAC & Off-gas system and electrical system including capacitor bank, UPS (un-interrupted power system) and generator set. Most of the equipment / units / systems are 30 years old and therefore have decreased performance. Therefore, it is necessary to optimize the operation of equipment / units / systems to regulate the operation of the equipment by considering its condition also to obtain performance at acceptable limits while maintaining safety and security. (author)
[en] Experiments to determine the effect of Nb element in the U-Zr alloys on hardness, microstructure and phase formation has been done. The addition of Nb element would effect the hardness, microstructure and phase which formed. The U-Zr-Nb alloy was made with the variation of Nb 2%, 5% and 8% by melting in an electric arc melting furnace that equipped with water cooling and the argon atmosphere. The U-Zr-Nb alloy to be cut divided to some testing, such as hardness test, microstructure, and phase analysis. Hardness testing was done by Vickers hardness testing equipment, microstructure by an optical microscope, and diffraction pattern by XRD and phase analysis was done by GSAS. Hardness testing results showed that the addition of 2% to 5% Nb element in U-Zr alloys will increased in hardness, but the addition of Nb element over 5% the hardness was decreased. Observations the microstructure showed that the addition of 2% to 5% Nb element, grains were formed from fine into coarse. Phase analysis for diffraction pattern showed that the phase changed from αU and γU (Zr,Nb)at 2% Nb to be αU, γU (Zr,Nb) and δ1 (UZr_2) phase at 5% and 8% Nb. Phase changes was followed by changes in its compositions. The composition of αU at 2% Nb was 40% increased to 81% at 5% Nb and decreased to 3.9% at 8% Nb. The composition of γU decreased from 59,86% to 14,91% with increased Nb from 2% to 5% and further increased to 52,74% at 8% Nb. (author)
[en] In order to improve water quality, and mitigate recurrent bio corrosion phenomena affecting the components of the Process Water System of the CNE, a combined water treatment adding a commercial biocide product, based on bromide, to the currently injected chlorine was proposed. The aim of this study was to evaluate the effect of the added biocide on the kinetics of biofilm formation and growth, which is the precursor process to microbiological corrosion, and on the corrosion rates of carbon steel of pipes, heat exchanger shells and other system devices. For this purpose, a test bench was designed and built, reproducing the flow conditions at certain parts of the system. This facility was installed in the filtration shed of the Water Plant of the CNE. The test bench consisted of two parallel chambers, I and II, each in turn divided into a section for determining biofilm growth and corrosion rates of carbon steel coupons and another one to measure the kinetics of biofilm growth on stainless steel coupons. Both chambers received lake water chlorinated for 15 minutes each day. The chamber II received also the biocide. The corrosion rate in carbon steel coupons was evaluated by weight loss and Linear Polarization Resistance (LPR) measurements. The kinetics of biofilm growth on carbon steel coupons was measured using disruptive methods followed by quantification of the protein and carbohydrate content as an estimation of total biomase. The following bacterial groups were quantified through the dilution-extinction method: total aerobic bacteria, acid-producing bacteria, total anaerobic bacteria, sulfate reducing bacteria and bacteria precipitating iron and manganese. On the stainless steel coupons, the percent of coverage was evaluated by epi fluorescence microscopy. The corrosion rate results obtained both by weight loss as by LPR, showed no significant differences between both chambers, with and without biocide. Regarding the kinetics of biofilm growth on carbon steel coupons, no significant differences between chambers were found. The analysis of the percentage of coverage on stainless steel coupons matches the results for carbon steel coupons. It was concluded that, under the current operating conditions, it is unlikely that the addition of a complementary biocide that acts by interaction with chlorine, could produce a beneficial effect of reduction and control of the biological material present in the water of the Process Water System of the CNE. It has been suggested to evaluate the possibility of revising the current chlorination scheme and improving its efficiency before implementing any complementary biocide addition scheme (author)
[en] In the frame of the deterministic approach in the safety analysis of the ITER reactor, it is postulated that a helium cooling line from the cryogenic system and one coolant pipe of the first wall/blanket primary heat transport system are damaged simultaneously in the cryostat. In the frame of the validation of the computer codes which are used for the assessment of ITER safety, the EVITA experiment has been designed for the simulation of the physical phenomena occurring during a coolant ingress into the cryostat. A simultaneous ingress of water/steam and non condensable gas can be simulated. The vacuum vessel of the EVITA facility contains a cryogenic plate. One of the main objectives of the experiments is to determine the steam condensation phenomena on this cryogenic plate. Major deliverables of the EVITA experiments are as follows: ice formation kinetics; heat transfer characteristics; condensed water mass; cryogenic surface temperature; dynamic pressure and temperature in vessel. The main data of the tests are initial pressure, temperature of the injected fluid, injected mass flowrate, initial temperatures of internal structures and operating conditions of the cryogenic loop. The tests are calculated using different computer codes namely PAXITR code. The comparison between calculations and experiments allows the ability of these computer codes to treat the relevant physical phenomena (heat transfer coefficient between walls and fluid, vessel pressurization, ice layer formation) to be assessed. The latest series of experiments, involving simultaneous water/steam and gas ingress have been performed with different configurations of the facility and different operating conditions. These tests have been carried out to obtain the ice layer formation kinetics. This paper presents the main results of the work done so far, emphasizing the interpretation of the tests and the consequent evolutions of the modelling used in the PAXITR code. They lead to a better evaluation of the pressure evolution in the vacuum vessel and of the ice layer formation. The EVITA program can provide a good contribution to the validation methodology for fusion safety analysis codes. (author)
[en] Highlights: • We present an innovative occupancy and chilled water storage-based operation mode. • This mode was implemented to the solar-assisted air-conditioning system. • It permits to save 42% of total electrical energy during one cooling period. • It allows storing the excess cooling capacity of the absorption chiller. • It prevents the sudden start/stop (on/off cycles) of the absorption chiller. - Abstract: This study describes an innovative occupancy and chilled-water storage-based operation sequence implemented in a solar-assisted air-conditioning system. The core purpose of this solar-assisted air-conditioning system is to handle the cooling and heating load of the Solar Energy Research Centre (CIESOL), thus minimising its environmental impact. In this study, the cooling mode was investigated with special attention focused on the chilled-water storage circuit. The critical concern is that the solar-assisted air-conditioning system should always operate considering the actual load conditions, not using an abstract maximum load that is predetermined during the system’s design process, which can lead to energy waste during periods of low occupancy. Thus, the fundamental problem is to identify the optimum operation sequence for the solar-assisted air-conditioning system that provides the best energy performance. The significance of this work lies in the demonstration of a new operation strategy that utilises real-time occupancy monitoring and chilled-water storage tanks to improve the efficiency of solar-assisted air-conditioning systems, thereby reducing their electricity consumption. Adopting this strategy resulted in a large energy-saving potential. The results demonstrate that during one cooling period, it is possible to conserve approximately 42% of the total electrical energy consumed by the system prior to the adoption of this operation strategy
[en] The results of experimental investigation of penning type charged particles source with metal-hydride water cooled cathode are presented. The feature of investigation is hydrogen ion-stimulated desorption from metal-hydride as a way of working gas feeding. The influence of ion-stimulated desorption on emissive source characteristics was studied. In outflowing in axial direction charged particles flow the dynamic of energy distribution function of electrons and ions was carried out and their dependence on discharge external parameters was determined.